#include <string.h>

void reverse(char* str)
{
  char* left = str;
  char* right = str + strlen(str) -1;
  char tmp;
  for(;left<right;++left,--right) {
    tmp = *left;
    *left = *right;
    *right = tmp;
  }
}

int main()
{
  char str[] = "abcedf";
  reverse(str);

  return 0;
}
